Edible oil solvent production

ABSTRACT

An improved process for the solvent extraction of aromatics from a mixture thereof with non-aromatics. Increased aromatic recovery and solvent purity in the lean solvent recycle to the extraction zone is afforded. The resulting non-aromatic raffinate stream is reduced in the concentration of aromatic hydrocarbons, particularly those having more than eight carbon atoms per molecule, and is suitable for use as an edible oil solvent.

United States Patent Stone May 13, 1975 EDIBLE OIL SOLVENT PRODUCTION3,436.435 4/1969 Van Tassell 208/321 3, 90,092 6 1971 U'tt' t l 2 8 32[75] Inventor: Richard D. Stone, Des Plaines,ll1. 5 I 1 .6 a 0 I 1 [73]Assignee: Universal Oil Products Company, Primary Examiner-HerbertLevine D65 P1311165, Altorney, Agent, or FirmJames R. Hoatson, Jr.; [22]Filed: Jan. 30, 1974 Robert W. Enckson; William H. Page, II

[21] Appl. No.: 438,073 ABSTRACT 1521 US. Cl. 208/321; 208/325; 208/333lmpmved pmFeSs for the emacm F matics from a mixture thereof wlthnon-aromatics. In- [51] Int. Cl ClOg 21/28 creased aromatic recover andsolvent um in the [58] Field of Search 208/321 Y y lean solvent recycleto the extraction zone is afforded. References Cited :The resultingnon-aromatic rafiinate stream IS reduced In the concentration ofaromatic hydrocarbpns, partic- UNITED STATES PATENTS ularly those havingmore than eight carbon atoms per 687,982 8/1954 Baumann .2 208/321molecule, and is suitable for use as an edible Oil sol- 2,923,680 2/1960Bushnell 208/321 vent, 3,119,767 1/1964 Scheibel 208/321 3.179.7084/1966 Penisten 2. 208/321 8 Claims, 1 Drawing Figure /3 9 LE fine/varWarn-Wash 8 Separation Zana l9 Ergo/Legion 1/ farm/amen! Sena/am! 4 f t30 3 f8 S/eom Gene/afar EDIBLE OIL SOLVENT PRODUCTION APPLICABILITY OFINVENTION This invention herein described is intended for utilization inthe separation, and ultimate recovery of polar hydrocarbons from amixture thereof with non-polar hydrocarbons, which separation iseffected through the use of a water-soluble solvent characteristicallyselective for adsorbing the polar hydrocarbons. More specifically, myinvention is directed toward the separation and recovery of aromatichydrocarbons from various mixtures thereof with non-aromatichydrocarbons.

My invention is particularly concerned with an improvement in the typeof separation process wherein a mixture of aromatic and non-aromatichydrocarbons is introduced into a solvent extraction zone. beingcountercurrently contacted therein with a solvent selective for theadsorption of the aromatic hydrocarbons. A raffmate phase, comprisingsubstantially all of the nonaromatic hydrocarbons in the feed stock (atleast about 90.0% by weight), is removed from one end portion of theextraction zone, and an extract phase comprising the aromatic componentsand the solvent is removed from the other end portion of the extractionzone, with the aromatic solute being recovered therefrom in a solventstripping zone through the utilization of steam. The hydrocarbon-leansolvent emanating from the solvent stripping column is recycled to theextraction zone wherein it further countercurrently contacts thehydrocarbonaceous feed mixture.

My invention is applicable for utilization with any hydrocarbon feedstock having a sufficiently high aromatic concentration to justify therecovery thereof i.e., at least about 25.0% by volume. As a generalrule, the overall carbon number range of suitable charge stocks is fromabout 6 to about 10, although both lower-hoiling and higher-boilingmaterial is often present. These charge stocks will include, in additionto C C and C -aromatics, non-aromatics, which can predominate in C and C-paraffms, C,,-plus aromatics and naphthcnic material. Typical ofvarious sources of suitable charge stocks constitutes the depentanizedeffluent from a naptha catalytic reforming unit, coke-oven by-products,resulting from the pyrolysis of naphtha to produce propylene, wash oils,etc.

My inventive concept is specifically directed toward the solventstripping facility integrated into a solvent extraction process. Theterm solvent stripping" is utilized to connote the technique wherein anaromaticrich solvent stream is contacted with steam to provide a solventconcentrate substantially free from hydrocarbons, a vaporous streamcomprising steam. solvent and hydrocarbons, and an aromatic concentratehaving a reduced solvent content and containing steam. The presenttechnique is particularly advantageous in that it affords additionalremoval of hydrocarbons, and particularly aromatic hydrocarbons havingmore than eight carbon atoms per molecule from the solvent concentrate.A distinct improvement is afforded when the solvent concentrate isrecycled for further utilization in the solvent extraction zone. As ageneral rule, approximately 50.0% of the aromatic hydrocarbons containedin the recycled solvent suffer from re-cntry loss; that is, theyultimately appear in the recovered rat'finate phase. This is ofsignificant import when the ultimate considered utilization of theraffmate phase is as a solvent for edible oils.

Within the food processing industry, it is common practice to extractedible oil from various food materials by contacting pulverizedparticles with a solvent and subsequently recovering the extracted oilby distillation or fractionation. Such food materials include corn,peanuts, soy beans, etc. Generally, the extracted oil is furtherpurified by contacting with caustic soda to effect the removal of fattyacids in order to further enhance the oil for human consumption. Thepurified oil is commonly referred to as edible oil." Suitable solventsfor use in extracting edible oils include-acetone, benzene, hexane,carbon disulfide, etc. One of the more common requirements for asatisfactory edible oil solvent is that it contains less than about 1.0%by volume of total aromatic hydrocarbons, and preferably less than 0.5%by volume, and less than about 10 ppm. by weight of the water-solublesolvent. With respect to the aromatic concentration of the edible oilsolvent, it is fur ther generally required that the same contain lessthan about 0. l0% by volume of the heavier aromatic hydrocarbons, orthose having more than eight carbon atoms per molecule. A suitablesource of edible oil solvent is the non-aromatic raffinate phaserecovered from a solvent extraction process, provided the aforementionedcriteria are met.

PRIOR ART It must be recognized that the prior art proliferatcs in awide spectrum of solvent extraction processes for effecting theseparation of aromatic hydrocarbons from a mixture thereof withnon-aromatic hydrocarbons. No attempt will be made herein to delineateexhaustively the appropriate published literature; it will sufficesimply to note several examples which appear to be exemplary of priorart practices and procedures, and to which the present invention is mostsuitably applicable. The greater majority of solvent extractionprocesses indicate a distinct preference for a water-soluble solventcomprising an oxygenated organic compound. A review of the relevantprior art indicates that the preva lent solvent is either asulfolane-type organic compound, or an alkylene glycol, preferably apoly-alkylene glycol. While most prior an processes are intended forutilization with either of these water-soluble solvents, specifictechniques have been illustrated which are peculiar either to one, orthe other.

Illustrations of solvent extraction processes may be typified by U.S.Pat. Nos. 3,466,346 (Cl. 260-674), 3,396,101 (Cl.208-3l3), and U.S. Pat.No. 3,520,946 (Cl. 260-674). U.S. Pat. No. 3,429,802 (Cl. 208-87)recognizes that an edible oil solvent can be produced from the raffmatestream recovered from a solvent extraction process. However, there is norecognition of the utilization of a low molecular weight paraffinichydrocarbon in the solvent stripping zone, but rather the addition of acatalytic hydrogenation reaction system which processes the as-producedraffinate stream.

OBJECTS AND EMBODIMENTS A principal object of my invention is directedtowards increased solvent purity of the lean solvent stream recovered ina stripping column integrated within a solvent extraction process. Acorollary objective resides in decreasing the quantity of aromatichydrocarbons, and particularly those having more than about eight carbonatoms per molecule, in the lean solvent stream recycled to the solventextraction zone.

A specific object of my invention affords the production of an edibleoil solvent containing less than about 0. l()% by volume of aromatichydrocarbons having more than about eight carbon atoms per molecule.

Therefore, in one embodiment, my invention affords a process forremoving aromatic hydrocarbons having more than eight carbon atoms permolecule from the extract phase from a solvent extraction zone, whichprocess comprises contacting said extract phase, containing (i) solvent,characteristically selective for ad sorbing aromatic hydrocarbons, (ii)aromatics contain ing less than nine carbon atoms per molecule and,(iii) aromatic hydrocarbons containing more than eight carbon atoms permolecule, with a lower molecular weight paraffinic hydrocarbon,containing from about three to about seven carbon atoms per molecule, ina stripping zone, and recovering said solvent reduced in theconcentration of aromatic hydrocarbons having more than eight carbonatoms per molecule.

In a specific embodiment, the present invention involves a process forpreparing a substantially aromaticfree edible oil solvent whichcomprises the steps of: (a) contacting a mixture of aromatic andnon-aromatic hydrocarbons with a water-soluble solvent, selective forthe dissolving of aromatic hydrocarbons, in a solvent extraction zone,to provide (i) a first solventrich extract stream and, (ii) asolvent-lean raffinate stream; (b) contacting said first extract streamwith a paraffinic hydrocarbon having from three to about seven carbonatoms per molecule, in a stripping zone; (c) recovering, from saidstripping zone, (i) a first vaporous stream containing said paraffinichydrocarbons, (ii) a vaporous, aromatic-rich stream, and, (iii) a secondsolventrich stream; (d) introducing said second solvent-rich stream intosaid solvent extraction zone, as said watersoluble solvent; and, (e)recovering said raffinate stream as said substantially aromatic-freeedible oil solvent.

These, as well as other objects and embodiments of my invention, willbecome evident from the following detailed description thereof. Briefly,however, with respect to such other embodiments, these involve operatingconditions, particular solvents, in-process separations and streamflows, preferredparaffinic hydrocarbons for utilization in the removalof aromatic hydrocarbons from the solvent stream to be recycled to thesolvent extraction zone, etc. For example, preferred solvents includealkylene glycols, polyalkylene glycols and sulfolane-type organiccompounds, while the preferred paraffinic hydrocarbons contain fromabout four to about six carbon atoms per molecule.

SUMMARY OF INVENTION Although applicable to a multitude of hydrocarbonaccous mixtures. further discussion will be limited to the separationof aromatic hydrocarbons from a mixture thereof with paraffins and/ornaphthenes, and the recovery of a nonaromatic raffinate stream suitablefor use as an edible oil solvent. Initially, the mixture of hydrocarbonsis contacted with a water-soluble, oxygencontaining solvent particularlyselective for the extraction ofthe aromatic hydrocarbons. There isrecovered an extract stream containing aromatic hydrocarbons and a majorproportion of the water-soluble solvent (more than about 99.0% byweight), and a raffinate stream containing non aromatic hydrocarbons anda relatively minor proportion (less than about 1.0%) of thewater-soluble solvent. The raffmate stream, also containing less thanabout l 0% by volume of total aromatic hydrocarbons, is generallycontacted, in countercurrent flow, with water to recover the selectedsolvent and to provide a hydrocarbon oncentrate substantially free fromsolvent. The extract stream is contacted with steam, in a solventstripping zone, to recover an aromatic hydrocarbon concentrate from thewater-soluble solvent. The latter is then recycled to the extractionzone for further use in extracting aromatic hydrocarbons from the chargestock.

The aromatic hydrocarbon concentrate is generally withdrawn, as aprincipally vaporous phase, from an intermediate portion of the solventstripping zone. As such, it contains significant quantities of steam andsolvent, as well as entrained liquid (principally solvent). Thisaromatic concentrate is introduced into an entrainment separator for theremoval of the greater pro portion of the entrained liquid phasetherefrom. The separated liquid phase is returned to the solventstripping zone, while the balance of the extract phase is condensed andintroduced into an extract receiver for separation into an aromatic-richproduct stream and a water concentrate.

In an alternative embodiment. not shown in the accompanying diagrammaticillustration, rich solvent from the extraction zone initially enters anextractive distillation zone and then a solvent recovery column. In theextractive distillation zone, additional lean solvent contacts richsolvent from the extraction zone. Nonaromatics present in the richsolvent are removed via extractive distillation, in which technique,nonaromatics have a higher than normal vapor pressure in the presence ofmany of the aromatic selective solvents, thus permitting removal ofsmall amounts of non-aromatics by distillation. Of course, thetemperature and pressure in an extractive distillation column are toolow to allow recovery of aromatics from the solvent; therefore, a secondcolumn is generally required to recover aromatic hydrocarbons from thesolvent. Accordingly, in this alternative embodiment, a recovery column,operating at either a higher temperature, or lower pressure, or both,recovers aromatic hydrocarbons as an overhead vapor fraction. Therecovery column is generally refluxed with condensed aromatichydrocarbons. Lean solvent is recovered from the bottom of this column,but steam stripping is required to remove aromatics from the solvent. Inthis alternative embodiment i.e., extractive distillation followed by asolvent recovery column the practice of the pres ent invention helpsremove the deleterious amounts of aromatic hydrocarbons which wouldotherwise remain in the lean solvent. In this alternative embodiment,paraffinic stripping augments steam stripping in the solvent recoverycolumn.

In accordance with the inventive concept of the present invention, alower molecular weight paraffinic hy drocarhon is utilized as thestripping agent in the stripping column. Preferably, the same isutilized in admixture with steam, with the mole ratio of paraffin tosteam being in the range of about U. l:l.() to about l0.0:l.0. Suitableparaffinic hydrocarbons contain from about three to about seven carbonatoms per molecule, and include propane, normal butane, isobutane,normal pcntane, isopentane, neopentane, hexane, isohexane, heptane andisoheptane. Preferred paraffinic hydrocarbons contain from about four toabout six carbon atoms per molecule.

Particularly preferred stripping agents are those paraffinichydrocarbons having four carbon atoms per molecule, since lighterhydrocarbons are difficult to condense at the low pressures generallyencountered in the stripping column. Stripping with hydrocarbons heavierthan those containing six carbon atoms per molecule, requires additionalheat input due to the greater heat of vaporization per mole, whichincreases the utility requirements of the unit. Also, heavier strippingagents cannot be readily separated from the extract via distillation,where separation is necessary to produce a very pure aromatic product.The reason for the peculiar effectiveness of these light paraffinicstripping agents is not fully understood. It is postulated that theeffectiveness is due, at least in part, to the presence of very largeamounts of aromatic-selective solvent which rejects all thingsparaffinic.

SOLVENTS AND OPERATING CONDITIONS Generally accepted solvents, havingsolubility selectivity for aromatic hydrocarbons, are water-soluble,oxygen-containing organic compounds. In order to be effective in asystem of extraction, such as the process provided by the presentinvention, the solvent component must have a boiling point substantiallygreater than the boiling point of water, which is added to the solventcomposition for the purpose of enhancing its selectivity; in general,the solvent must also have a boiling point substantially greater thanthe end boiling point of the hydrocarbon feed stock. In most instances,the solvent has a greater density than the hydrocarbon feed stock and isaccordingly introduced into the uppermost portion of the solventextraction zone, thereafter flowing downwardly, countercurrently to therising hydrocarbon feed stock which is introduced into the extractionzone at about its mid-point.

Organic compounds, suitable as the solvent, may be selected from therelatively large groups of compounds characterized generally asoxygen-containing compounds, particularly the aliphatic and cyclicalcohols, the glycols and glycol ethers. Monoand polyalkylene glycols,in which the alkylene group contains from about two to about four carbonatoms, such as ethylene glycol, diethylene glycol, triethylene glycol,tetraethylene glycol, propylene glycol, dipropylene glycol, andtripropylene glycol, constitute a particularly preferred class oforganic solvents,

Another suitable class of selective solvents are those commonly referredto in the art as the sulfolane-type. This is a solvent having afive-membered ring, one atom of which is sulfur, the other four beingcarbon, and having two oxygen atoms bonded to the sulfur atom. Many ofthe solvents may be illustrated by the following formula:

R HCH-R wherein R, R R and R are independently selected from the groupconsisting of a hydrogen atom, an alkyl group having up to carbon atoms,and alkoxy radicals having up to eight carbon atoms and an arylalkylradical having up to 12 carbon atoms. Other solvents preferably includedare the sulfolenes such as 2- sulfolene or 3-sulfolene which have thefollowing structures:

Still other solvents having a high selectivity for separating aromaticsfrom non-aromatic hydrocarbons are 2- methylsulfolane,2,4-dirnethylsulfolane, methyl 2- sulfonyl ether, and 2-sulfonylacetate.

The aromatic selectivity of the selected solvent is further enhancedthrough the addition of water. Preferably, the solvent contains a smallamount of water dissolved therein to increase the selectivity of thesolvent phase for aromatic hydrocarbons over non-aromatic hydrocarbons,without reducing substantially the solubility of the solvent phase foraromatic hydrocarbons. The solvent composition contains from about 0.5%to about 25.0% by weight of water, and preferably from about 3.0% toabout l5.0%, depending on the particular solvent utilized and theprocess conditions under which the extraction zone and solvent stripperare operated. By the inclusion of water in the solvent composition, thesolubility of aromatic hydrocarbons in the solvent, although somewhatreduced in comparison with a non-aqueous solvent, decreases thesolubility of raffinate components in the solvent and the solubility ofsolvent in the raffinate stream. Solvent recovery from the raffinatestream may be accomplished efficiently by countercurrently washing theraff'mate with water in a separate washing zone from which an aqueouswash effluent is recovered containing the solvent. During steady-stateoperations, water washing reduces the solvent concentration in theraffinate stream from about 500 ppm. by weight to less than about l0.0ppm.

The solvent extraction zone is operated at elevated temperatures and ata sufficiently elevated pressure to maintain the hydrocarbonaceous feedstock, solvent and backwash streams in the liquid phase. Suitabletemperatures are within the range F. to about 400F., and preferably anintermediate level from about l75F. to about 300F. Pressures aregenerally within the range of about atmospheric up to about 400 psig.,and preferably from about 50 psig. to about I50 psig. Generally, thevolume of backwash introduced into the lower point of the extractionzone is at least 10.0% by volume of the extract phase emanatingtherefrom. The solvent to hydrocarbon feed volumetric ratio is in therange of l.0:l,0. to about l5.0:l.0, and preferably from about 2.0:l.0to about l0.0: L0.

The stripping column functions at moderate pressures and sufficientlyhigh reboiler temperatures to drive all the backwash non-aromaticcomponents and some of the aromatics, water and solvent overhead.Stripping pressures are from atmospheric to about psig., although thetop of the stripper is generally maintained at from about 1.0 psig. upto about 20.0 psig. The reboiler temperatures dependent upon thecomposition of the feed stock and the solvent, and are generally in therange of from 275F. to about 360F.

Other operating conditions will be given in conjunction with thedescription of one embodiment of the present invention as illustrated inthe accompanying drawing. Miscellaneous appurtenances, the descriptionof which is not believed required. by those possessing the requisiteexpertise in the appropriate art. have been eliminated from the drawing.The use of details such as pumps. compressors. controls andinstrumentation. heat-recovery circuits. valving. start-up lines andsimilar hardware. etc., is well within the purview of those skilled inthe art. It is understood that the illustration does not limit myinvention beyond the scope and spirit of the appended claims.

DESCRIPTION OF DRAWING The accompanying drawing is presented for thesole purpose of illustrating the method of integrating the presentinventive concept into a solvent extraction process which is designed toseparate and recover aromatic hydrocarbons from a mixture thereof withnonaromatic hydrocarbons. With reference now to the drawing. the freshfeed charge stock. for example a C plus fraction separated from theeffluent of a naphtha catalytic reforming unit. is introduced via line 1into solvent extraction zone 2. The charge stock contains about 41.0% byweight of paraffins. 4.0% naphthenes and 55.0% aromatic hydrocarbons. Asolvent-rich stream. containing less than 0.l85 molv total aromatichydrocarbons, and less than 0. l% aromatic hydrocarbons containing morethan eight carbon atoms per molecule. is introduced into extraction zone2 by way of line 3 in an amount such that the solvent to hydrocarbonfeed volumetric ratio is about 5.25: l .0; this solvent stream containsapproximately 6.0% by weight of water. A light hydrocarbon backwashstream. from line 4, is introduced into a lower portion of theextraction zone and serves to strip the heavier non-aromatichydrocarbons from the solventrich extract stream withdrawn by way ofline 5.

A first raffmate stream, containing about 0.09% total aromatics, and0.05 mol.% heavier aromatics. and solvent in an amount of about 500 ppm.by weight. is withdrawn by way of line 6 and introduced thereby into alower portion of water-wash column 7. A first water stream, containing aminor amount of both solvent and aromatic hydrocarbons, the latter beingless than about 0.1%. and substantially free from non-aromatichydrocarbons (less than about 0.01% is introduced into an upper portionof water-wash column 7 by way of line 8. A second raffinate phase,containing less than about 10 ppm. by weight of solvent. is removed fromthe process by way of line 9. A second water stream, containing thesolvent in the first water stream and that removed from the firstraffinate stream. and both dissolved and entrained non-aromatichydrocarbons. is withdrawn by way of line 10 and introduced via line 1]into separation zone 12.

Also introduced into separation Zone 12. in admixture with the secondwater stream in line 10. is a substantially pure first aromatichydrocarbon from line 28, the source of which is hereinafter set forth.A second aromatic stream. containing at least 90.0% of the non aromatichydrocarbons in the second water stream. is withdrawn from an upperportion of separation zone 12 by way of line 13. while a third Waterstream substantially free from non-aromatic hydrocarbons is withdrawn byway of line 14.

The third water stream is utilized to generate steam in steam generator15, employing the solvent-rich first extract stream in line 5 as theheat-exchange medium. In some operations. rich solvent from theextraction zone is not hot enough to be used as a heat exchange medium.In this event. hot lean solvent from the stripping column may be used asa heat exchange medium in steam generator 15. Normal butane. in anamount such that the mole ratio of normal butane to steam. enteringsteam generator 15, is 50.02500. is introduced into the process by wayof line 30. The cooled extract stream is introduced by way of line 17into solvent stripping zone 18, wherein it countercurrently contacts thegenerated steam being introduced by way of line 16. The solventconcentrate, containing less than 0.10 mol.% of heavier aromatics, isremoved by way of line 3 and recycled therethrough to solvent extractionzone 2. A principally vaporous phase. containing steam, hy drocarbonsand solvent is withdrawn by way of line 19, admixed with the secondaromatic stream in line 13, and introduced via line l9 into stripperreceiver 20.

The second extract stream. of reduced solvent content (about 2.5% byweight), concentrated in aromatic hydrocarbons and containing steam. iswithdrawn from an intermediate portion of stripping column 18 by way ofline 21. The second extract stream, at a temperature of about 220F.,containing entrained liquid. is introduced into separator 22, from whichentrained solvent is withdrawn by way of line 23 for re-introductionthereby into stripping column 18. A third extract stream. containingabout 0.5% solvent. is introduced through line 24 into condenser 25,wherein the temperature is decreased to a level of about 140F. The condensed third extract stream is passed via line 26 through extractreceiver 27. from which a fourth water stream. containing substantiallyall the solvent in the third extract stream. is removed by way of line 8and preferably recycled. at least in part. as the first water streamintroduced into water-wash column 7. The substantially pure aromaticconcentrate is withdrawn through line 28. In one embodiment. at least aportion continues through line 28 to serve as the substantially purefirst aromatic stream combined with the second water stream in line 11.The aromatic concentrate product of the process is withdrawn by way ofline 29.

Stripper receiver 20 serves to provide a light hydrocarbon backwashstream in line 4 which is introduced into the lower portion ofextraction zone 2 as hereinbefore set forth. A fifth water stream iswithdrawn by way of line 11, admixed with the second water stream inline 10, the mixture continuing through line 11 into separation Zone 12.

Without the addition of butane. via line 30, to steam generator 15, thelean solvent recycle in line 3 to extraction zone 2 contains totalaromatics in an amount of 0.344 mol.% and 0159 mol.% heavier, C plusaromatics. Furthermore. the solvent concentration of the total stream is97.25 mol.%. When the stripping vapors in line 16 are generatedutilizing the 50/50 mixture of butane and steam, as hereinaboveillustrated. the total aromatic hydrocarbon content is decreased to 0.lmol.7(. that of the heavier aromatics to a level of 0.098 mol."/( andthe solvent content is increased to 98.7l7av Therefore. as hereinbeforeset forth. since approximately onehalf of the aromatics entering theextraction zone 2 by way of line 3 suffer from reentry loss. and appearin the raffinate stream in line 6. only about 0.05 mol.7( heavieraromatics appear in the edible oil solvent produced as the raffinatestream in line 9.

The foregoing indicates the method by which the present invention isutilized to separate and recover an aromatic concentrate substantiallyfree from both solvent and non-aromatic hydrocarbons. The resultingedible oil solvent clearly meets the contaminant level limitation aspreviously stated.

Alternatively, the amount of stripping steam in line 16 may be decreasedwith the substitution therefor of a light paraffinic stripping agent ofthe present invention. With reduced stripping steam, the lean solventwill contain about the same level of impurities as in typical prior artschemes, however, the stripping of heavy aromatic hydrocarbons will havebeen effected with lesser utility requirements than prior art processes.This is because the heat required to vaporize one mole of C or Cparaffins is less than that required to vaporize one mole of water. If arefiner wants to make unleaded gasoline, he can tolerate, and frequentlyrequires, the presence of butanes in his gasoline to satisfy octane andvolatility requirements. Accordingly, butanes used as stripping agentscan be left in the extract product without detrimental effect, and mostimportant, without increasing water circulation rates in the process.This is in contrast to prior art processes where water recovered fromthe extract fraction contains too much expensive solvent to permitdisposal, so all water has to be recycled and it is virtually impossibleto increase stripping action in the stripping column withoutsimultaneously increasing steam flow thereto.

I claim as my invention:

1. A process for removing aromatic hydrocarbons having more than eightcarbon atoms per molecule from the extract phase from a solventextraction zone. which process comprises countercurrently contactingsaid extract phase, containing (i) solvent, characteristically selectivefor dissolving aromatic hydrocarbons, (ii) aromatics containing lessthan nine carbon atoms per molecule and, (iii) aromatic hydrocarbonscontaining more than eight carbon atoms per molecule, with a mixture ofsteam and a lower molecular weight paraffinic hydrocarbon, containingfrom about three to about seven carbon atoms per molecule, the moleratio of paraffin to steam in said mixture being in the range of about0.1 l .0 to about 10.0: 1 .0, and recovering said solvent reduced in theconcentration of aromatic hydrocarbons having more than eight carbonatoms per molecule.

2. The process of claim 1 further characterized in that said paraffinichydrocarbon contains from four to about six carbon atoms per molecule.

3. The process of claim 1 further characterized in that said paraffinichydrocarbon is a butane.

4. The process of claim 1 further characterized in that said paraffinichydrocarbon is a pentane.

5. A process for preparing a substantially aromaticfree edible oilsolvent which comprises the steps of:

a. contacting a mixture of aromatic and non-aromatic hydrocarbons with awater-soluble solvent, selec tive for dissolving aromatic hydrocarbons,in a solvent extraction Zone, to provide (i) a first solventrich extractstream and, (ii) a solvent-lean raffinate stream;

b. countercurrently contacting said first extract stream with a mixtureof steam and a paraffinic hydrocarbon having from three to about sevencarbon atoms per molecule, the mole ratio of paraffin to steam in saidmixture being in the range of about 0.1:].0 to about [00:10, in astripping zone,

c. recovering, from said stripping zone, (i) a first vaporous streamcontaining said paraffinic hydrocarbons, (ii) a vaporous, aromatic-richstream and, (iii) a second solvent-rich stream;

d. introducing said second solvent-rich stream into said solventextraction zone, as said water-soluble solvent; and

e. recovering said raffinate stream as said substantially aromatic-freeedible oil solvent.

6. The process of claim 5 further characterized in that saidwater-soluble solvent is a polyethylene glycol.

7. The process of claim 5 further characterized in that saidwater-soluble solvent is a sulfolane-type compound.

8. The process of claim 5 further characterized in that said aromatichydrocarbons comprise both aromatics having less than nine and more thaneight carbon atoms per molecule.

1. A PROCESS FOR REMOVING AROMATIC HYDROCARBONS HAVING MORE THAN EIGHTCARBON ATOMS PER MOLECULE FROM THE EXTRACT PHASE FROM A SOLVENTEXTRACTION ZONE, WHICH PROCESS COMPRISES COUNTERCURRENTLY CONTACTINGSAID EXTRACT PHASE, CONTAINING (I) SOLVENT, CHARACTERISTICALLY SELECTIVEFOR DISSOLVING AROMATIC HYDROCARBONS, (II) AROMATICS CONTAINING LESSTHAN NINE CARBON ATMOS PER MOLECULE AND, (III) AROMATIC HYDROCARBONSCONTAINING MORE THAN EITH CARBON ATOMS PER MOLECULE, WITH A MIXTURE OFSTEAM AND A LOWER MOLECULAR WEIGHT PARAFFINIC HYDROCARBON, CONTAININGFROM ABOUT THREE TO ABOUT SEVEN CARBON ATOMS PER MOLECULE, THE MOLERATIO OF PARAFFIN TO STEAM IN SAID MIXTURE BEING IN THE RANGE OF ABOUT0.1:1.0 TO ABOUT 10.0:1.0, AND RECOVERING SAID SOLVENT REDUCED IN THECONCENTRATION OF AROMATIC HYDROCARBONS HAVING MORE THAN EIGHT CARBONATOMS PER MOLECULE.
 2. The process of claim 1 further characterized inthat said paraffinic hydrocarbon contains from four to about six carbonatoms per molecule.
 3. The process of claim 1 further characterized inthat said paraffinic hydrocarbon is a butane.
 4. The process of claim 1further characterized in that said paraffinic hydrocarbon is a pentane.5. A process for preparing a substantially aromatic-free edible oilsolvent which comprises the steps of: a. contacting a mixture ofaromatic and non-aromatic hydrocarbons with a water-soluble solvent,selective for dissolving aromatic hydrocarbons, in a solvent extractionzone, to provide (i) a first solvent-rich extract stream and, (ii) asolvent-lean raffinate stream; b. countercurrently contacting said firstextract stream with a mixture of steam and a paraffinic hydrocarbonhaving from three to about seven carbon atoms per molecule, the moleratio of paraffin to stEam in said mixture being in the range of about0.1:1.0 to about 10.0:1.0, in a stripping zone; c. recovering, from saidstripping zone, (i) a first vaporous stream containing said paraffinichydrocarbons, (ii) a vaporous, aromatic-rich stream and, (iii) a secondsolvent-rich stream; d. introducing said second solvent-rich stream intosaid solvent extraction zone, as said water-soluble solvent; and e.recovering said raffinate stream as said substantially aromatic-freeedible oil solvent.
 6. The process of claim 5 further characterized inthat said water-soluble solvent is a polyethylene glycol.
 7. The processof claim 5 further characterized in that said water-soluble solvent is asulfolane-type compound.
 8. The process of claim 5 further characterizedin that said aromatic hydrocarbons comprise both aromatics having lessthan nine and more than eight carbon atoms per molecule.